1. Technical Field
The present invention relates to an angular velocity sensor and an angular velocity and acceleration detecting composite sensor, which are particularly used in attitude control or a navigation system of a mobile body, such as an aircraft and a vehicle.
2. Background Art
FIG. 15 is a sectional view of a conventional angular velocity sensor. Referring to FIG. 15, the conventional angular velocity sensor generally has a structure, in which angular velocity sensor element 102 and IC 103 that controls angular velocity sensor element 102 are disposed in package 101. Recently, there has been proposed a structure in which, in order to suppress transmission of a disturbance vibration applied to package 101 to angular velocity sensor element 102, angular velocity sensor element 102 is placed in an internal space of package 101 while suspended by vibration-proof member 104.
In angular velocity sensor element 102, angular velocity sensor element 102 is mounted on vibration-proof member 104 with seat 105 interposed therebetween in order to ensure a vibrating space to detect an angular velocity, while a vibration type element is used to detect a flexural component of the element from a Coriolis force associated with an angular velocity applied about a detection axis when the driving vibration of the element is performed.
FIG. 16 is a schematic diagram illustrating a vibrating state of the angular velocity sensor element in the conventional angular velocity sensor. Referring to FIG. 16, when angular velocity sensor element 102 is mounted on seat 105 placed on a surface of vibration-proof member 104, a barycentric position of angular velocity sensor element 102 attached to package 101 with vibration-proof member 104 interposed therebetween is higher than a surface of vibration-proof member 104. Therefore, as illustrated by arrow 106, a flexural vibration is excited in vibration-proof member 104 in response to the disturbance vibration applied to package 101 from an outside, and the flexural vibration is mistakenly detected as an angular velocity of rotation about the detection axis.
FIG. 17 is an exploded perspective view of the conventional angular velocity sensor. FIG. 18 is a horizontal sectional view of the conventional angular velocity sensor. FIG. 19 is a perspective view of an accommodation unit in the conventional angular velocity sensor when viewed from below. FIG. 20 is a perspective view of a case in the conventional angular velocity sensor when viewed from above. FIG. 21 is a perspective view of the case in the conventional angular velocity sensor when viewed from below.
Referring to FIGS. 17 to 21, in case 230, multilayer circuit board 231 having a layer structure including ceramic and a wiring conductor is provided from an inner bottom surface to an outer bottom surface, and first wiring electrode 232 and second wiring electrode 233 are provided in an upper surface of multilayer circuit board 231 as illustrated in FIG. 20. IC 235, which is electrically connected to first wiring electrode 232 through wire 234 made of gold or aluminum, and capacitor 236, which is electrically connected to second wiring electrode 233, are provided in the upper surface of multilayer circuit board 231. IC 235 is accommodated in case 230, and processes an output signal outputted from vibrator 221. As illustrated in FIG. 21, six case electrodes 237 made of silver are provided on an outer bottom surface of multilayer circuit board 231 in case 230. As illustrated in FIG. 20, sidewall 238 made of ceramic is provided in an outer periphery of the upper surface of multilayer circuit board 231, and metal frame 239 made of kovar is provided on the upper surface of sidewall 238. As illustrated in FIG. 20, step portion 240 is provided in the inner bottom surface of case 230, third wiring electrodes 241 are provided in step portion 240 while vibrator 221 in FIG. 17 is fixed to step portion 240, and third wiring electrodes 241 are electrically connected to vibrator 221 through wire 234. An opening of case 230 is sealed by a metallic lid 242 such that the inside of case 230 becomes a vacuum atmosphere. Accommodation unit 243 made of resin is configured such that a direction perpendicular to an opposing board (not illustrated) that is a measured object of the angular velocity is set to a sensing axis of the angular velocity. Case 230 is accommodated in accommodation unit 243, and one end of each of at least three terminals 244, in which the other end is electrically connected to vibrator 221, is integrally buried in case 230. Placing unit 245 is provided in substantially parallel to the sensing axis of the angular velocity in accommodation unit 243 while located in a substantial center of accommodation unit 243, and case 230 is placed on placing unit 245. One end sides of terminals 244 are buried in placing unit 245, and leading end portions 244a on one end sides of terminals 244 are exposed from placing unit 245.
Case 230 is placed on placing unit 245 in accommodation unit 243, whereby case electrodes 237 in case 230 are electrically connected to leading end portions 244a on one end sides of terminals 244 in placing unit 245. Because leading end portions 244a on one end sides of terminals 244 are mechanically connected to case 230, case 230 is configured to be supported from an outside by terminals 244 in each of which the other end is integrally buried in accommodation unit 243.
As illustrated in FIG. 19, six electrode recesses 246 are provided in the outer bottom surface of accommodation unit 243, and the leading end portions on the sides of the other ends of terminals 244, which are integrally buried in accommodation unit 243, are exposed to electrode recesses 246 to provide supply electrode 247, GND electrode 248, output electrode 249, and three fixing electrodes 250. As illustrated in FIG. 18, Z-shape bending portion 244b is provided in the substantial center of each of six terminals 244, and Y-axis-direction extended portion 251 and Z-axis-direction extended portion 252 are provided by bending portion 244b, whereby case 230 is configured to be displaced in an X-axis direction with respect to accommodation unit 243. As illustrated in FIG. 19, three recesses 253 are provided in the outer bottom surface of accommodation unit 243. As illustrated in FIG. 19, in metallic cover 254, three latching pawls 256 are provided on the opening side, and the latching pawls 256 are swaged at recesses 253 in accommodation unit 243 illustrated in FIG. 19, thereby providing GND potential connection portion 255 in the outer bottom surface of accommodation unit 243 as illustrated in FIG. 19.
An operation of the conventional angular velocity sensor having the above configuration will be described below.
When vibrator 221 rotates at angular velocity ω about a center axis (sensing axis) in a longitudinal direction while performing flexion movement at an eigenfrequency, a Coriolis force of F=2 mV×ω is generated in an arm of vibrator 221. The output signal including a charge is inputted to IC 235 by the Coriolis force through wire 234, third wiring electrode 241, multilayer circuit board 231, first wiring electrode 232, and wire 234, and waveform processing is performed to the output signal. The output signal is inputted to an target computer (not illustrated) through second wiring electrode 233, capacitor 236, case electrode 237, leading end portion 244a on one side of terminal 244, terminal 244, and output electrode 249 to detect the angular velocity.
Assuming that a vibration in the X-axis direction is applied from the outside, case 230 is bent in the X-axis direction with respect to accommodation unit 243 because Y-axis-direction extended portion 251 and Z-axis-direction extended portion 252 are provided in terminal 244 in the conventional angular velocity sensor. Therefore, the X-axis-direction disturbance vibration applied from the outside is damped so as not to propagate to case 230.
For example, PTL 2 is well known as citation list information on the invention of the subject application.
However, in the above conventional configuration, because case 230 is bent in the X-axis direction with respect to accommodation unit 243, although the X-axis-direction disturbance vibration applied from the outside can be damped so as not to propagate to case 230, Y-axis-direction and Z-axis-direction vibrations applied from the outside cannot be damped.
FIG. 22 is an exploded perspective view of a conventional angular velocity and acceleration detecting composite sensor. FIG. 23 is a side sectional view of the conventional angular velocity and acceleration detecting composite sensor. FIG. 24 is a perspective view of an angular velocity detection element in the conventional angular velocity and acceleration detecting composite sensor. FIG. 25 is a perspective view of the conventional angular velocity and acceleration detecting composite sensor.
Referring to FIGS. 22 to 25, angular velocity detector 301 includes vibrating body 302 that is constructed by a tuning fork, in which single-crystal quartz thin films having different crystal axes are bonded to each other as illustrated in FIG. 24, case 303 that accommodates vibrating body 302, and lid 304 that closes an opening (not illustrated) provided in an upper surface of case 303. Driving electrodes 305 are provided on a frontside surface and a backside surface of vibrating body 302 constituting angular velocity detector 301, and detection electrodes 306 are provided on an outer side surface and an inner side surface of vibrating body 302. Case 303 constituting angular velocity detector 301 accommodates vibrating body 302 therein, and the opening (not illustrated) is provided in the upper surface of case 303. As illustrated in FIG. 22, supply terminal 307, angular velocity output terminal 308, and GND terminal 309 are provided in lid 304 constituting angular velocity detector 301 so as to pierce lid 304 from the upper surface to the lower surface, and one end of each of supply terminal 307 and GND terminal 309 is electrically connected to driving electrode 305 of vibrating body 302. One end of angular velocity output terminal 308 provided in lid 304 is electrically connected to detection electrode 306 of vibrating body 302.
In acceleration detector 311 in which an acceleration signal processing IC (not illustrated) is incorporated, a movable electrode plate (not illustrated) and a fixed electrode plate (not illustrated) are provided, and supply terminal 312, X-axis acceleration output terminal 313a, Y-axis acceleration output terminal 313b, and GND terminal 314, in each of which one end is electrically connected to the movable electrode plate (not illustrated) and the fixed electrode plate (not illustrated), are provided so as to project outward. Reference numeral 315 denotes a circuit board, angular velocity detector 301 is fixed to a lower surface of circuit board 315, many terminal insertion holes 316 are made from the upper surface to the lower surface of circuit board 315, and supply terminal 307, angular velocity output terminal 308, and GND terminal 309 of angular velocity detector 301 are inserted in terminal insertion holes 316. Acceleration detector 311 is fixed to the lower surface of circuit board 315, and angular velocity signal processing IC 317 including an electronic component in which an AGC circuit (not illustrated) is provided is provided in the upper surface of circuit board 315. Supply terminal 307, angular velocity output terminal 308, and GND terminal 309 of angular velocity detector 301 and supply terminal 312, X-axis acceleration output terminal 313a, Y-axis acceleration output terminal 313b, and GND terminal 314 of acceleration detector 311 are electrically connected to angular velocity signal processing IC 317.
Shielded case 318 includes metallic accommodation unit 318a and lid 318c that closes opening 318b of accommodation unit 318a. Shielded case 318 accommodates circuit board 315, angular velocity detector 301, and acceleration detector 311 therein, and power relay terminal 319, GND relay terminal 320, angular velocity relay terminal 321, X-axis acceleration relay terminal 322, and Y-axis acceleration relay terminal 323 are provided in shielded case 318 so as to pierce from the inside to the outside. In shielded case 318, one end of power relay terminal 319 is electrically connected to supply terminal 307 of angular velocity detector 301 and supply terminal 312 of acceleration detector 311, and one end of GND relay terminal 320 is electrically connected to GND terminal 309 of angular velocity detector 301 and GND terminal 314 of acceleration detector 311. One end angular velocity relay terminal 321 is electrically connected to angular velocity output terminal 308 of angular velocity detector 301, one end of X-axis acceleration relay terminal 322 is electrically connected to X-axis acceleration output terminal 313a of acceleration detector 311, and one end of Y-axis acceleration relay terminal 323 is electrically connected to Y-axis acceleration output terminal 313b of acceleration detector 311. Biasing portions 324 constructed by elastic protrusions, each of which is formed by making a cut in a perpendicular portion 318d, are provided in lid 318c of shielded case 318. Lid 318c is elastically crimped in an outer side surface of opening 318b of shielded case 318 by biasing portions 324, whereby accommodation unit 318a is set to the same potential as lid 318c. 
Resin protective case 325 having a cylindrical shape with a bottom accommodates shielded case 318 therein, connector 326 is provided in protective case 325 so as to project outward from the side surface, one end of each of power connector terminal 327, angular velocity connector terminal 328, X-axis acceleration connector terminal 329, Y-axis acceleration connector terminal 330, and GND connector terminal 331 is provided inside connector 326, and the other end is buried in protective case 325. As illustrated in FIG. 25, through-holes 332 are made in protective case 325 from the bottom surface to the outer bottom surface, and the other end of each of power connector terminal 327, angular velocity connector terminal 328, X-axis acceleration connector terminal 329, Y-axis acceleration connector terminal 330, and GND connector terminal 331 is located in through-hole 332 made in protective case 325. The other end of X-axis acceleration relay terminal 322 is inserted in a hole (not illustrated) of X-axis acceleration connector terminal 329 of protective case 325, and electrically connected by solder 335. The other end of Y-axis acceleration relay terminal 323 is inserted in a hole (not illustrated) of Y-axis acceleration connector terminal 330, and electrically connected by solder 335. The other end of power relay terminal 319 is inserted in a hole (not illustrated) of power connector terminal 327, and electrically connected by solder 335. The other end of angular velocity relay terminal 321 is inserted in a hole (not illustrated) of angular velocity connector terminal 328, and electrically connected by solder 335. The other end of GND relay terminal 320 is inserted in a hole (not illustrated) of GND connector terminal 331, and electrically connected by solder 335. Resin protective lid 336 closes the opening provided in the upper surface of protective case 325.
An operation of the conventional angular velocity and acceleration detecting composite sensor configured and assembled as described above will be described below.
A DC voltage of an externally-provided power supply (not illustrated) is converted into an AC voltage by power connector terminal 327, power relay terminal 319, and angular velocity signal processing IC 317, and the AC voltage is applied to driving electrode 305 of vibrating body 302 of angular velocity detector 301 through supply terminal 307. Similarly, driving electrode 305 is grounded through GND connector terminal 331, GND relay terminal 320, and GND terminal 309, whereby vibrating body 302 performs a flexion vibration. At this point, when angular velocity detector 301 rotates at angular velocity ω about the center axis in the longitudinal direction of vibrating body 302, the Coriolis force of F=2 mv×ω is generated in vibrating body 302. The output signal including the charge generated in detection electrode 306 by the Coriolis force is converted into an output voltage through angular velocity output terminal 308 by angular velocity signal processing IC 317 of circuit board 315, and the output voltage is inputted to the target computer (not illustrated) through angular velocity relay terminal 321 and angular velocity connector terminal 328 to detect the angular velocity. Similarly, when the acceleration is applied in the X-axis direction and the Y-axis direction, which are directions horizontal to a plane of acceleration detector 311, while 5 V is applied to the movable electrode plate (not illustrated) and the fixed electrode plate (not illustrated) of acceleration detector 311 through power connector terminal 327, power relay terminal 319, and supply terminal 307, the movable electrode plate (not illustrated) moves to change a capacity of a capacitor provided between the movable electrode plate (not illustrated) and the fixed electrode plate (not illustrated). The change in capacity is converted into the output voltage in acceleration detector 311, and the acceleration in the X-axis direction is inputted to the target computer (not illustrated) through X-axis acceleration output terminal 313a, X-axis acceleration relay terminal 322, and X-axis acceleration connector terminal 329 to detect the acceleration in the X-axis direction. Similarly, the acceleration in the Y-axis direction is inputted to the target computer (not illustrated) through Y-axis acceleration output terminal 313b, Y-axis acceleration relay terminal 323, and Y-axis acceleration connector terminal 330 to detect the acceleration in the Y-axis direction. The angular velocity applied to the vehicle body, acceleration in the X-axis direction, and the acceleration in the Y-axis direction are analyzed by the target computer (not illustrated) to analyze a behavior of the vehicle body.
For example, PTL 3 is well known as citation list information on the invention of the subject application.
However, in the conventional configuration, because supply terminal 307, angular velocity output terminal 308, and GND terminal 309 of angular velocity detector 301 are rigidly fixed to circuit board 315, the flexion vibration of vibrating body 302 in angular velocity detector 301 is directly transmitted to acceleration detector 311 through circuit board 315. When the movable electrode plate of acceleration detector 311 moves, the acceleration output signal is detected even though the acceleration is not generated.